CSLB General Building (B) — All Questions
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According to Ohm's law, voltage equals current multiplied by:
- a.power
- b.capacitance
- c.resistance✓
- d.frequency
Ohm's law states that voltage equals current times resistance, written as V equals I times R. This relationship links the three basic quantities in a circuit.
The unit used to measure electrical resistance is the:
- a.volt
- b.ampere
- c.watt
- d.ohm✓
Resistance is measured in ohms, symbolized by the Greek letter omega. The volt measures voltage, the ampere measures current, and the watt measures power.
A device that stores electrical charge is a:
- a.capacitor✓
- b.resistor
- c.inductor
- d.transformer
A capacitor stores electrical energy in an electric field between two plates. A resistor limits current, while an inductor stores energy in a magnetic field.
In a circuit, current is measured in:
- a.ohms
- b.amperes✓
- c.volts
- d.farads
Electric current, the flow of charge, is measured in amperes, often shortened to amps. Ohms measure resistance, volts measure voltage, and farads measure capacitance.
What is the total resistance of two 10-ohm resistors connected in series?
- a.5 ohms
- b.10 ohms
- c.20 ohms✓
- d.100 ohms
In a series circuit, resistances add together directly. Ten ohms plus ten ohms equals 20 ohms. In parallel, the total would instead be lower than either resistor.
Electrical power in watts is calculated by multiplying voltage by:
- a.resistance
- b.time
- c.capacitance
- d.current✓
Power equals voltage times current, written as P equals V times I. This gives the rate at which electrical energy is used, measured in watts.
A component that allows current to flow in only one direction is a:
- a.diode✓
- b.resistor
- c.capacitor
- d.switch
A diode conducts current in one direction and blocks it in the other, acting like a one-way valve. This property makes diodes useful for converting AC to DC.
The abbreviation AC stands for:
- a.automatic circuit
- b.alternating current✓
- c.ampere current
- d.active charge
AC stands for alternating current, in which the direction of electron flow reverses periodically. DC, or direct current, flows steadily in one direction.
Which material is the best conductor of electricity?
- a.Rubber
- b.Glass
- c.Copper✓
- d.Wood
Copper is an excellent conductor and is widely used in electrical wiring. Rubber, glass, and wood are insulators that resist the flow of current.
A transformer is used to change the level of:
- a.resistance
- b.frequency
- c.current direction
- d.voltage✓
A transformer increases or decreases AC voltage using two coils of wire. Stepping voltage up or down helps electricity travel efficiently and power different devices.
If voltage is 12 volts and resistance is 4 ohms, what is the current?
- a.3 amperes✓
- b.2 amperes
- c.4 amperes
- d.48 amperes
Using Ohm's law, current equals voltage divided by resistance. That is 12 volts divided by 4 ohms, which equals 3 amperes.
A material that strongly resists the flow of electric current is called a(n):
- a.conductor
- b.insulator✓
- c.semiconductor
- d.battery
An insulator resists the flow of electricity and is used to protect and separate conductors. Rubber and plastic are common insulators used to coat wires.
The component that provides a source of stored electrical energy in a portable device is the:
- a.fuse
- b.switch
- c.battery✓
- d.antenna
A battery stores chemical energy and converts it to electrical energy to power a device. A fuse protects the circuit, and a switch simply opens or closes it.
A fuse protects a circuit by:
- a.increasing the voltage
- b.storing extra charge
- c.reversing the current
- d.breaking the circuit when current is too high✓
A fuse contains a thin wire that melts and breaks the circuit when current exceeds a safe level. This prevents overheating and damage to the rest of the circuit.